When the natural lens of the human eye becomes physically damaged or has some disease necessitating its removal, such as a cataract, it is often replaced with an artificial intraocular lens.
During the process of surgically implanting such lens through an incision at the edge of the cornea, it has been found that static touching of the corneal endothelium with a polymethylmethacrylate (PMMA) or other surgical tool, can permanently destroy a portion of the endothelial cells. It is generally recognized that the human endothelium, which is only one cell layer thick, cannot regenerate itself by producing additional cells. It appears that more damage is done to the corneal endothelium by a dynamic or sliding contact with such lens or tool during surgery as compared to a static or nonsliding contact with the endothelium. The corneal endothelium is very critical to the eye as it is a barrier between the outer layers of the cornea and the aqueous humor in the anterior chamber. After surgery, the location of the intraocular lens is such that, when in its proper position, it does not contact or damage the corneal endothelium.
It has been suggested by others to coat the intraocular lens with methylcellulose (MC) or polyvinylpyrrolidone (PVP). The following publications describe such coating.
Kaufman, H. E. and J. I. Katz, "Endothelial Damage From Intraocular Lens Insertion," Inv. Ophth., Vol. 15(12), December 1976, p. 996-1000 PA1 Kaufman, H. E., Jeffrey Katz, et al, "Prevention of Endothelial Damage From Intraocular Lens Insertion," Tr. Am. Acad. Ophth. & Otol., Vol. 83, March-April 1977, p. 204-212 PA1 Kaufman, H. E. and J. I. Katz, "Pathology of the Corneal Endothelium," Inv. Ophth. Visual Sci., Vol. 16(4), April 1977, p. 265-268 PA1 Fechner, P. U., "Methylcellulose in Lens Implantation," Jour. Amer. Intraocular Implant Society, Vol. 3(3 & 4), July-October 1977, p. 180-181 PA1 Kaufman, H. E., Jeffrey Katz, et al, "Corneal Endothelium Damage with Intraocular Lenses: Contact Adhesion Between Surgical Materials and Tissue," Science, Vol. 198(4316), November, 4, 1977, p. 525-527.
While the above coatings of MC and PVP helped protect the corneal endothelium during surgery, they had several shortcomings. A supply of methylcellulose used by Dr. Kaufman in the above publications was obtained from him and tested. It was found to be a very poor film former and tended to "bead up" on the PMMA lens exposing edges of the lens. It has been found that MC has a very fast dissolution rate. Dipping of lenses in MC or PVP is useful to protect the corneal endothelium. However, because of the fast dissolution rate of these polymers and the difficulty of placing a controlled amount of such polymers on the lenses, the extent and length of time of protection is uncontrollable. Because of the wet and slippery nature of lenses dipped during surgery, the lenses are difficult to handle and a portion of the coating may drip off. In addition, MC and PVP solutions must be sterilized prior to dipping. The amount and type of contact with the corneal endothelium varies with the skills and techniques of different ophthalmic surgeons. It is highly desirable to have a coating that protects against both static and dynamic sliding contact.